Field of the Invention
This invention relates to an apparatus and method for performing medical bacteriology and clinical chemistry by means of changes in turbidity, color or other optical properties which serve as indicators of biological activity, content or condition of the specimen under investigation. More particularly, this invention relates to an apparatus for automatically and continuously determining the rate of the bacterial growth by photometric means.
The specimen may be a biological fluid recovered from a patient, such as serum, plasma, urine, cerebrospinal fluid, acities or an artificially prepared nutrient or reagent fluid capable of supporting or demonstrating phenomena correlative to pathological, physiological, chemical, or metabolic state, activity or content.
Current clinical practice in medical microbiology and bacteriology is largely concerned with the isolation and evaluation of pathogenic bacteria from specimens of clinical interest. Such specimens may be derivative of both the patient, for example his blood, urine, wound exudate, or other biological fluid, or his immediate or etiological environment, such as food, air, water, or other factors of an infection or communicable disease vector system. Concomitant with the identification of a viral, mycotic, or bacterial pathogen agent in a specimen is the requirement for determining what antibiotic agent is effective against a specific pathogen and to what degree it is effective in comparison to other chemotherapeutic agents available to the clinician as treatment of the condition.
Assay of biological fluids for levels of antibiotic, in vivo, also falls within the scope of medical microbiology, although the performance of the procedure is far less frequent than the above-described identifications of antibiotic effectiveness or sensitivity, a term derived from the subject organism's "sensitivity" to a drug. The assay procedure is extremely difficult to perform under presently available conditions in the laboratory and as such it is used only in research or in cases of extreme clinical importance. Although the information derived from such a procedure is very valuable to the clinician, it is an abnormally severe imposition on the laboratory staff.
The determination of minimum inhibitory concentration (MIC) of the antibiotic effectiveness against a particular pathogen also falls within the scope of medical microbiology, although not performed as often as antibiotic sensitivity.